Tube extrusion apparatus including separable arrested mandrel tip tube cutoff

ABSTRACT

Tube extrusion apparatus employing an arrested mandrel having a separable tip including axially spaced extrusion and cutoff portions. The mandrel tip is substantially smaller than the main mandrel which supports the tip during billet piercing operation resulting in back extrusion of the billet material. The mandrel is stationary during the extrusion operation and at the completion advances slightly to introduce the tube cutoff portion of the mandrel tip into the extrusion die.

United States Patent Inventors John W. Isott Dearbom, Mich.; Harold E.Honkala; Delbert V. Carraher, Decatur, Ala. App]. No. 765,406 Filed Oct.7, 1968 Patented May 25, 1971 Assignee Universal Oil Products CompanyDes Plaines, Ill.

TUBE EXTRUSION APPARATUS INCLUDING SEPARABLE ARRESTED MANDREL TIP TUBECUTOFF 7 Claims, 11 Drawing Figs.

US. Cl 72/255, 72/265, 72/273 Int. Cl. B2lc 23/00 Field of Search72/254, 255, 265

References Cited UNITED STATES PATENTS 861 ,194 7/ 1907 Schwieger 72/265 Primary ExaminerRichard J. Herbst Assistant Examiner-A. L. HavisAttomey-Whittemore, l-lulbert & Belknap ABSTRACT: Tube extrusionapparatus employing an arrested mandrel having a separable tip includingaxially spaced extrusion and cutoff portions. The mandrel tip issubstantially smaller than the-main mandrel which supports the tipduring billet piercing operation resulting in back extrusion of thebillet material. The mandrel is stationary during the extrusionoperation and at the completion advances slightly to introduce the tubecutoff portion of the mandrel tip into the extrusion die.

Patented May 25, 1971 4 Sheets-Sheet 1 INVENTORS H 1 mi l-AWN z p.ATTORNEYS BY M Patented May 25, 1971 3,580,037

4 Sheets-Sheet 3 z o FIGB 42 l/ 41a is T F|G9 A .0

v INVENTORS JOHN w. ISSOTT HARO E. HONKALA DELBE v. CARRAHER f u I 1 BY1% 2 41 ATTORNEYS Patented May 25, 1971 4 Sheets-Sheet 4 VENT )R 5 INOTT ONKA JOHN w. 'ss HAROLD E H DELBERT V.CARRAHER BY r v(17K;

ATTORNEYS TUBE EXTRUSION APPARATUS INCLUDING SEPARABLE ARRESTED MANDRELTIP TUBE CUTOFF BRIEF SUMMARY OF THE INVENTION Briefly described, theapparatus performs a tube extrusion operation normally from the solidbillet, but possibly with a previously apertured billet. A main mandrelis employed extending through the billet container which is relativelylarge, at least substantially larger than the internal diameter of theextrusion die. Carried at the forward end of the main mandrel is aremovable and replaceable mandrel tip having at least two portions ofdifferent diameter. The leading one of these two portions is dimensionedto be received within the throat of the die and to determine wallthickness of the extruded tube. During the extrusion operation thisportion of the mandrel tip, which is referred to herein as the extrusionportion, remains in a stationary positionin the throat of the die. A ramnormally operating through an annular pressure pad, pushes the materialof the billet forwardly over the relatively large main mandrel and intothe restricted portion adjacent the entrance into the die and eventuallythrough the throat of the die around the extrusion portion of themandrel. At the completion of the extrusion operation the main mandrelwith the removable tip is moved forwardly a short distance causing thecutoff portion of the mandrel tip to enter into the throat of the die.This cutoff portion has a diameter very slightly smaller than theinternal diameter of the throat and its entrance into the die results insevering the rear end of the extruded tube from the portion of thebillet remaining in the container.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 14 are plan views, partly insection, showing the critical components of the tube extrusion apparatusin the positions which the parts reach sequentially during tubeextrusion.

FIGS. 59 are sectional views generally diagrammatic in character,showing positions reached sequentially by the mandrel and mandrel tip.

FIG. is a sectional longitudinal view through the mandrel tip.

FIG. 11 is an end view of the mandrel tip.

DETAILED DESCRIPTION The present invention is concerned primarily with anovel mandrel and removable and replaceable mandrel tip, but in order tounderstand the operation and advantages of the mandrel and particularlythe mandrel tip, it is considered desirable to briefly review thecomplete tube extrusion apparatus.

Referring first to FIGS. l-4 there is shown a plan view with parts insection showing the essential operating components of tube extrusionapparatus. This apparatus comprises a stationary die 10 having acircularopening 12-therethrough suitably supported in die supportstructure indicated generally at 14 which includes a chamber orcontainer 16 for the reception of a billet 18 of the material from thetube is to be extruded. Ordinarily, the billet 18 is in the form of asolid cylindrical body although if desired, it may initially have anopening extending axially therethrough. It will be understood that thedisclosure in these FIGS. is more or less diagrammatic and that theactual container for the billet may be a separate sleeve formed of amaterial capable of resisting the scouring effect of the metal of thebillet as it is caused to flow. Ram and piercing mechanism is providedeffective to initially force a mandrel assembly comprising an elongatedrelatively large main mandrel 20 and a detachable and replaceablemandrel tip 22 through the billet so as to position the mandrel tip 22in a proper position for extrusion. The mandrel tip, as willsubsequently appear, includes a reduced extrusion or sizing portion 24adapted to be positioned and maintained in fixed relation within thethroat of the die to determine the internal diameter of the tube duringextrusion. The mandrel tip also includes a relatively larger cutoffportion 26 whose diameter is only slightly smaller than the internaldiameter of the die and which is effective, when the mandrel assembly ismoved slightly forwardly upon completion of the extrusion operation tosever the extruded tube from the portion of the billet remaining in thecontainer.

The mechanism for carrying out the tube piercing and extrusionoperations comprises a cylinder 28 having a movable piston 30 thereinconnected through rod structure 32 to the main mandrel 20, Connected tothe rod structure is guide and abutment means 34 engageable withretractable stop elements 36 for purposes which will presently bedescribed. A main ram cylinder 38 is provided in which there is a mainram 40 movable longitudinally therein upon the introduction of hydraulicfluid under pressure into the cylinder 38. The main ram 40 is solidlyconnected to an annular ram sleeve 42 which is adapted to apply pressureto the rear end of the billet through an annular dummy block or pressurepad 44. The abutments 36 are each connected to pistons 46 slidable incylinders 48 between the operative position illustrated in FIG. I andthe retracted positions illustrated in FIG. 4. The guide and abutmentmeans 34 is slidable longitudinally on rods 50 which carry adjustablestop nuts 52. The stop elements or abutments 36 are generally U-shapedand in the position illustrated in FIG. 1, straddle the rod 50 and areengageable at one side with the stop nuts 52.

At this time hydraulic pressure is admitted to the cylinders 28 and 38.Admission of pressure to the cylinder 28 moves the piston 30 forwardlyto bring the forward end of the mandrel tip 22 into a position adjacentthe billet 18. At the same time, the admission of pressure into thecylinder 38 moves the main ram 40 forwardly so that the dummy block 44and possibly the extreme forward end of the ram sleeve 42 enters theopening 16 in the die support. The position of the extrusion apparatusjust described is illustrated in FIG. 2.

The next succeeding operation is the admission of further fluid pressureto the cylinder 28, advancing the piston 30 to a position determined bythe engagement between the guide and abutment means 34 with theabutments 36. This position must be determined with considerableaccuracy since it serves to locate the forward reduced extrusion portion24 within the throat of the die 10 so as to define therewith an annularspace which determines the size of the extruded tubing. At this time theram sleeve 42 and the dummy block 44 remain in fixed position. Aspreviously described, the main mandrel which supports the mandrel tip isrelatively larger than the mandrel tip and since a substantial portionof the main mandrel enters the container 16, back extrusion of thematerial of the billet 18 occurs. The relationship of parts at thisjuncture in the operation is illustrated in FIG. 3. A plug which hasbeen separated from the material of the billet and pushed through thedie ahead of the mandrel tip is illustrated at 54.

This conditions the apparatus for the commencement of the actualextrusion. This is accomplished by the introduction of hydraulic fluidunder pressure into the cylinder 38, forcing the ram 40 to the left asillustrated in FIG. 4. During this advance of the ram and ram sleeve 42,the mandrel is retained in stationary position by the abutment 36 andthe material of the billet is caused to flow around the inner end of themain mandrel and across the diminishing diameters of the mandrel tip andthence outwardly through the die into tubular form as determined by thepresence of the reduced extrusion portion of the mandrel tip within thethroat of the die.

When the ram sleeve 42 and the dummy block 44 reach a position closelyadjacent to the die, the extrusion operation is complete and all thatremains to be done is to separate the extruded tube from the remainingmetal of the billet. This is accomplished by actuating the piston andcylinder device 46, 48 to retract the abutment 36 to the positionillustrated in FIG. 4, thus permitting the guide and abutment means 34to move forwardly a distance equal to the thickness of the stop 36 intoengagement with the adjustable stop nut 52. This permits a slightfurther advance movement of the mandrel and permits the cutoif portion26 of the mandrel tip to enter into the throat of the die, thus severingthe rear end of the extruded tube from the remaining material of thebillet.

In FIG. 5 it will be observed that the forward end of the reducedmandrel tip 22 is directly adjacent the rear end of the billet l8 andthat in this position the dummy block 44 has just entered the rear endof the container 16, thus closing it. The advancing movement of themandrel 20 results in piercing the billet and some backward displacementor extrusion of the billet due to its elongation as seen in FIG. 6. Atthe same time, this operation results in placing the forward reducedextrusion portion 24 of the mandrel tip within the throat of the diewhere it remains during the complete extrusion operation.

In FIG. 7 the extrusion operation is illustrated as partially completed,the mandrel 20 having remained in the same position illustrated in FIG.6 while the ram sleeve 42 and dummy block 44 have advanced to extrudematerial from the billet 18 into the tubing illustrated at T.

In FIG. 8 the parts are shown in the position corresponding to the endof the extrusion operation, at which time further movement of the ramsleeve 42 to the right has terminated.

In FIG. 9 the ram sleeve is shown as slightly withdrawn, dummy block 44remaining in its furthest advanced position, and the main mandrel 20 hasadvanced slightly to bring the enlarged tube cutoff portion 26 of themandrel tip into the throat of the die 10, thus performing a tube cutoffoperation severing the rear end of the tube T from the remainingmaterial of the billet 18.

Referring now to FIGS. 10 and 11 there is shown the detailedconstruction of the removable mandrel tip 22. As shown in these FIGS.the tip is provided with a through opening 60 which terminates in asmall passage 62, as for example approximately three thirty-seconds ofan inch which permits cooling fluid to escape from the interior of themandrel and particularly, to permit steam to pass to the interior of thefinished tube as it moves beyond the die. At its rear end of the mandreltip 22 has an enlarged radial flange 64 provided with a concave fillet66 at its forward portion and provided rear wardly of a flat radialsurface 68 with threads as illustrated at 70. Intermediate the threadsand the flat surface 68 is a cylindrical pilot surface 72 which isdimensioned to fit accurately within a piloting recess provided at theforward end of the main mandrel 20. Accordingly, the mandrel tip will befirmly attached to the forward end of the mandrel and will be locatedaccurately thereon by engagement between the cylindrical pilot surface72 and the flat locating surface 68 thereof with correspondingaccurately formed piloting and locating surfaces on the main mandrel.The forward reduced extrusion portion 24 of the mandrel tip is connectedto the somewhat larger tube cutoff portion 26 by a gradually inclined orconica portion 74.

In order to facilitate the operation of the mandrel tip 22 in its billetpiercing operation, forwardly of the extruded portion the mandrel tiphas a first reduced portion 76 and a further reduced portion 78. Theforward end of the otherwise cylindrical extrusion portion 24 of themandrel tip is slightly tapered as indicated at 79, as for example tothe 1 cone angle indicated. The forward end of the mandrel tip isconcave as indicated at 80. This arrangement facilitates piercing of thebillet as well as a back extrusion of the material, as best illustratedin FIG. 6.

In FIG. 11 it will be observed that flats 82 are provided at oppositesides of the mandrel tip which cooperate with a wrench for screwing andunscrewing the tip with respect to the main mandrel.

In practice the diameter of the tube cutoff portion 26 may for example0.0l0 inch smaller than the internal diameter of the throat of the die10. This results in a reduction in thickness of the material of the tubeto an extent where it is effectively severed from the material of thebillet.

The present construction has several important practical advantages overconventional tube extrusion apparatus. By employing a relatively largeand therefore quite strong and rigid main mandrel, mandrel structurecapable of piercing substantially longer billets is provided. This is avery important practical advantage since it results in the extrusion oflonger lengths of tubing and further results in the extrusion of agreater percentage of a billet into the tubular extrusion. In practice,significant advantages are obtained when the main mandrel has a diametersubstantially larger than the diameter of the cutoff portion of themandrel tip and preferably, the diameter of the main mandrel is at least20 percent greater than the diameter of the cutoff portion of theextrusion tip. In a practical embodiment of the present invention,diameter of the cutoff portion of the mandrel tip was approximately1.990 inches, and the diameter of the main mandrel was 2.624 inches.Thus, it will be observed that the main mandrel has a diameter 0.634inch greater than the diameter of the cutoff portion of the mandrel tip,representing an increase in diameter of over 30 percent. This in turnrenders the main mandrel substantially more rigid than a mandrel capableof advance during the extrusion operation and hence, suggesting anelongated extrusion portion substantially equal in length to the mainmandrel of the present invention.

The drawings and the foregoing specification constitute a description ofthe improved tube extrusion apparatus including separable arrestedmandrel tip tube cutoff, in such full, clear, concise and exact termsas'to enable any person skilled in the art to practice the invention,the scope of which is indicated by the appended claims.

We claim:

1. Tube extrusion apparatus comprising a billet container, an annulardie having an open throat at the front of said container, a ram forapplying extrusion pressure to a billet in said container to extrudematerial thereof through said die, and mandrel structure extendingthrough said container into the throat of said die, said mandrelstructure comprising an elongated main mandrel of a cross section areasubstantially exceeding the cross section area of said die throat, aremovable and replaceable mandrel tip at the forward end of said mainmandrel having a short forward substantially cylindrical extrusionportion dimensioned to be received in the die throat with a clearancedeterminative of the wall thickness of tubing extruded thereover and ashort slightly enlarged cylindrical cutoff portion behind said extrusionportion dimensioned to enter the throat of the die and to sever theextruded tubing, and means for arresting said mandrel structure with theforward extrusion portion of said mandrel tip in said die throat andretaining said mandrel structure in fixed position during extrusion, andfor thereafter providing limited additional advance of said mandrelstructure to move said cutoff portion into said die throat.

2. Apparatus as defined in claim 1 in which the extrusion and cutoffportions of said tip are connected by a short gradually tapered portionto facilitate flow thereover during extrusion.

3. Apparatus as defined in claim 1, the means for arresting said mandrelstructure and thereafter providing limited additional advance comprisingfixed abutment means, stop means movable with said mandrel means, andmovable abutment means selectively movable into position between saidfixed abutment means and said stop means to arrest said mandrelstructure with said extrusion portion in said die throat and movable outof such position to provide for further advance of said mandrelstructure until said stop means engages said fixed abutment means andsaid cutoff portion enters said die throat.

4. Apparatus as defined in claim 1, in which said extrusion or sizingportion of said mandrel tip is slightly tapered forwardly at about 1from a true cylindrical form.

5. Apparatus as defined in claim 1, said main mandrel having a threadedrecess at its forward end, said mandrel tip having a threaded rearextension received in said recess and an annular thrust surfacesurrounding said threaded extension and directly engaging the end ofsaid main mandrel.

6. Apparatus as defined in claim 1, said main mandrel having a diameterat least 20 greater than the diameter of the eutoff portion of themandrel tip.

7. The method of extruding a tube which comprises supporting a mandreltip having a forward sizing portion and a following slightly largercutoff portion at the front end of a heavy main mandrel having adiameter substantially larger than that of said cutoff portion,positioning an elongated billet in a container having a die at itsforward end, forcing the main mandrel forwardly to pierce the billet toelongate the billet by back-extrusion,.to position the sizing portion ofthe tip in said die, and to position the forward end of said mainmandrel to occupy a substantial portion of the billet, extruding thematerial of said billet by applying pressure to the rear of said billetthus causing the material of the billet to flow forwardly along the mainmandrel and along the cutoff portion of the mandrel tip and thencethrough the die and along the sizing

1. Tube extrusion apparatus comprising a billet container, an annulardie having an open throat at the front of said container, a ram forapplying extrusion pressure to a billet in said container to extrudematerial thereof through said die, and mandrel structure extendingthrough said container into the throat of said die, said mandrelstructure comprising an elongated main mandrel of a cross section areasubstantially exceeding the cross section area of said Die throat, aremovable and replaceable mandrel tip at the forward end of said mainmandrel having a short forward substantially cylindrical extrusionportion dimensioned to be received in the die throat with a clearancedeterminative of the wall thickness of tubing extruded thereover and ashort slightly enlarged cylindrical cutoff portion behind said extrusionportion dimensioned to enter the throat of the die and to sever theextruded tubing, and means for arresting said mandrel structure with theforward extrusion portion of said mandrel tip in said die throat andretaining said mandrel structure in fixed position during extrusion, andfor thereafter providing limited additional advance of said mandrelstructure to move said cutoff portion into said die throat.
 2. Apparatusas defined in claim 1 in which the extrusion and cutoff portions of saidtip are connected by a short gradually tapered portion to facilitateflow thereover during extrusion.
 3. Apparatus as defined in claim 1, themeans for arresting said mandrel structure and thereafter providinglimited additional advance comprising fixed abutment means, stop meansmovable with said mandrel means, and movable abutment means selectivelymovable into position between said fixed abutment means and said stopmeans to arrest said mandrel structure with said extrusion portion insaid die throat and movable out of such position to provide for furtheradvance of said mandrel structure until said stop means engages saidfixed abutment means and said cutoff portion enters said die throat. 4.Apparatus as defined in claim 1, in which said extrusion or sizingportion of said mandrel tip is slightly tapered forwardly at about 1*from a true cylindrical form.
 5. Apparatus as defined in claim 1, saidmain mandrel having a threaded recess at its forward end, said mandreltip having a threaded rear extension received in said recess and anannular thrust surface surrounding said threaded extension and directlyengaging the end of said main mandrel.
 6. Apparatus as defined in claim1, said main mandrel having a diameter at least 20* greater than thediameter of the cutoff portion of the mandrel tip.
 7. The method ofextruding a tube which comprises supporting a mandrel tip having aforward sizing portion and a following slightly larger cutoff portion atthe front end of a heavy main mandrel having a diameter substantiallylarger than that of said cutoff portion, positioning an elongated billetin a container having a die at its forward end, forcing the main mandrelforwardly to pierce the billet to elongate the billet by back-extrusion,to position the sizing portion of the tip in said die, and to positionthe forward end of said main mandrel to occupy a substantial portion ofthe billet, extruding the material of said billet by applying pressureto the rear of said billet thus causing the material of the billet toflow forwardly along the main mandrel and along the cutoff portion ofthe mandrel tip and thence through the die and along the sizing portionof the mandrel tip therein while maintaining the sizing portion withinsaid die, and finally severing the extruded tube from the remainder ofsaid billet by advancing the main mandrel and mandrel tip to move thecutoff portion into the die.